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~ \ 220 REPORT OF SECRETARY protection to the crop against drought. The protection to the crop against droughit is. in . almost exact proportion to. the total available soil water within reach of. the crop." This was found particularly true for the small grains in the drier years. During the 16 years that the Station has been under operation the water stored by summer-tillage has more than doubled the yield of winter wheat as compared with wintel' wheat following small grain. Many years during the 16. only enough, water was accumulated to moisten two or three feet of soiL It is not claimed that water. in storage will completely produce a crop, but it will tend to carry it thru a drought. There' aIje very leV!" years when there is '.not sufficient. rainfall so that with moisture in storage in the soil satisfactory crops al'e. obtained. L. L. Zook, in Nebraska Experiment Station Bul. 192, (8, p. 2.) says: "Average yields per acre of all crops were . higher on . fallow than under any system of contin'uous cropping. Yilelds of grain on failow were frequently mOl'e than double those of grain after grain.. Of crops grown on fallow the largest gains were made by winter wheat and the smallest by corn." In . Circular No. 72, Kansas State AgricuLtural College (4), George S. Knapp reports: "Experiments at the Garden. City Branch Experiment Station, covering a period. of five years; have shown that sufficient .water 'can be stored in the soil by win~er irrigation alone .to proiluce good crops of com, kafir, milo, .and certain row crops. The soil on which\l;heseexperiments were made is a deep silt, loam, representative of most of the upland in. the western part of the state. Good yields have been obtained each year with all crops grown on the winter irrigated land. At the same time with the exception of the wet ~eason of 1915; unirrigated land produced prae. tically nothing.'~ Abundant evidence as to the value of water either stored or as a <:lirectapplication, might be presented but it seems hardly necessary . to do it in vie\yof the fact that it is now so generally recognized that water is the limiting factor in crop production in the area. known as the Great Plains. The question now comes' whether or not the soils. of this pal,ticulararea have the ability to hold the water effici~ntlY when it is applied. .\ Soils of the Area. . .. . . The soil of the proposed irrigation area is .all of loessial ongm. The loess material below the line of soil de\'elopment is' of general uniform composition and texture and extends to a depth of 100 feet or more without any faults such as rock strata, hard pan, or gravtel seams. It lies upon a bed of water bearing' sand, which seems to i mderlie the entire loess plains. Below the sand is the. Pierre Shale of C~etaoeous age. . The only variation thruout the depth of the loess -.... ~ -. . e-:.;